Synagrops japonicus is a species of ray-finned fish within the family of Synagropidae.
[4] It can be found from Eastern Africa up to the islands of Hawaii.
[2] They have 10 dorsal spines, 9 dorsal soft rays, 2 anal spines, 7 anal soft rays, and 25 vertebrae.
The body is elongated and compressed with large cycloid scales.
The body is blackish-brown when young, though after maturing into adults, it becomes paler.